如何从文本文件中删除特定行？

Question

I have two.txt files. One contains a list of domains (google.com, facebook.com, apple.com, amazon.com), each on a separate line. The other one contains a smaller list of domains (facebook.com, amazon.com), which are also each on a separate line.

I want to remove all the domains which are on the second text file, from the first text file.

So for example, the first text file would go from

google.com
facebook.com
apple.com
amazon.com

To:

google.com
apple.com

How could this be done with a python script?

Answer 1

Try with this one.

f = open("text1.txt")
list1 = [i.strip() for i in f.readlines()]
f.close()
f = open("text2.txt")
list2 = [i.strip() for i in f.readlines()]
f.close()
def Diff(list1, list2):
    return list(set(list1) - set(list2)) + list(set(list2) - set(list1))
list1 = Diff(list1, list2)
f = open("text1.txt","w")
for i in list1:
    f.write(f"{i}\n")
f.close()

Answer 2

Fast answer and stub:

with open('filename1.txt', 'r') as f:
  text1 = f.read()
with open('filename2.txt', 'r') as f:
  text2 = f.read()
with open('filename1.txt', 'w') as f:
  domains = text1.splitlines()
  keep_domains = text2.splitlines()
  new_domains = [d for d in domains if d in keep_domains]
  text = '\n'.join(new_domains)
  f.write(text)

This solution could work fine.

Note: I dislike method.readlines() of file object, I prefer string method.splitlines because first one keeps new line characters. I dislike to use 'r+' mode when reading/writing file, I prefer to make it separately.

Answer 3

Python Diff To get a diff using the difflib library, you can simply call the united_diff function on it. For example, Lets say you have 2 files, file1 and file2 with the following content: Now to take their diff use the following code: This will give the output:

def Diff(li1, li2):
    return list(set(li1) - set(li2)) + list(set(li2) - set(li1))

li1 = ['google.com','facebook.com','apple.com','amazon.com']
li2 = ['facebook.com','amazon.com']

print(Diff(li1, li2))

Compare Two Text Files

file1 = "path to file"
file2 = "path to file"

import difflib
with open('file1') as f1:
    f1_text = f1.read()
with open('file2') as f2:
    f2_text = f2.read()
# Find and print the diff:
for line in difflib.unified_diff(f1_text, f2_text, fromfile='file1', tofile='file2', lineterm=''):
    print line